The development of synkinesis after facial nerve paralysis

In this study, the development of clinical synkinesis after facial nerve paralysis (FP) and its relationship to electrophysiological findings were investigated. Thirty-four patients who were examined within the first 5 days after onset of FP and who could also be followed up for at least 4 months were included in the study. Electrophysiological investigations consisted of: (1) recording of the direct responses by facial nerve stimulation at the stylomastoid fossa; (2) recording of the 'synkinetic spread' of the supraorbital nerve reflex to the lower facial muscles; (3) recording of the 'lateral spread responses' by stimulating the mandible and zygomatic branches of the facial nerve. Clinical synkinesis developed in 14 of 18 patients (78%) with a direct response ratio (DRr) of less than 40%. Among the 16 patients with a DRr of 40% or more, synkinesis was observed in 3 cases (18.7%) only. The DRr provided reliable information concerning the development of synkinesis. Forty percent seemed to be a reasonable limit to distinguish the high-risk group for the development of clinical synkinesis.